1. Field of the Invention
The present invention concerns cable pullers. More particularly, the invention is directed to an adjustable cable puller for accommodating cables while transferring the cable via a tray pre-installed in an enclosed space (including under floor ducts, cellular floors, conduits, raised floors, ceiling zones and cable trays) without tangling the cables.
2. Description of the Prior Art
Copper wires and optical fibers are widely used in utility transmission and communication to permit power or digital data transmission over long distances and at high data rates. Optical fibers are also used to form sensors, and in a variety of other applications. Multi-mode fibers are used mostly for short distances (up to 500 m), and single-mode fibers are used for longer distance links. In practical fibers, a cladding is usually coated with a tough resin buffer layer, which may be further surrounded by a jacket layer, usually plastic. These layers add strength to the fiber but do not contribute to its optical wave guide properties. For indoor applications, the jacketed fiber is generally enclosed, with a bundle of flexible fibrous polymer strength members, in a lightweight plastic cover to form a simple cable. Each end of the cable may be terminated with a specialized optical fiber connector to allow it to be easily connected and disconnected from transmitting and receiving equipment. Modern fiber cables can contain up to a thousand fibers in a single cable, so the performance of optical networks easily accommodates even today's demands for bandwidth on a point-to-point basis.
It is necessary to pull fiber optic cables via inner ducts in a ceiling or other spaces of a building. These are usually straight pulls (point A to point B). There are some commercially available fiberglass wire pulling rods which are used to fish cables through walls and floors, over suspended ceiling grid and into many other hard to reach areas. The fiberglass rods have a degree of flex which allows for bending through wall outlet holes and stud holes. Once the rod hooks the cables, the user pulls the cables across the enclosed space.
However, if the space was left with a drag line therein when the building was being constructed, a person can find the drag line, tire the drag line to a plurality of cables, then to pull the other end of the drag line from another side of the enclosed space to pull the cables via the enclosed space. The process becomes easies if there is another person feeding the cables from the first side of the enclosed space. When considering directly attaching the drag line to the cables, loose fiberglass threads are not suitable for direct attachment because they may break if knotted. Fiberglass epoxy rods are too rigid to tie, but may be secured to the pulling fixture by using tight clamping plates or screws.
More modern buildings are installed with air plenums, trays, or raceways. For example, some cable trays are manufactured in a 2″×2″ grid pattern with 0.120 inch wire diameter. The smaller grid helps to prevent cable sagging or dropping when used in fiber optic applications. These trays are available in widths of 2″, 4″, 6″, 8″, and 10″ and depths of 2″ and 4″. The available lengths are 1, 2, 5, 8, and 10 feet. Others come with a grid pattern of 2″×4″ and are available in standard widths of 6″, 8″, 12″, 18″ and 24″. Lengths can be ordered in 1′, 2′, 5′, 8′ and 10′ with a depth/height of either 2″ or 4″. Diagonal pulling across an area or pulling around a corner used to require professional skills to install the cable at an angle. However, tray junctions make changing routing directions easy. Each type tray junction is available in 2 or 4 inch deep trays and 6, 8, 12, 18 and 24 inch widths. U.S. Pat. No. 6,193,217 describes a cable puller to work with such trays.
The product marked with U.S. Pat. No. 6,193,217 and carried by Zimmer's Communication Inc. were no longer available in the market. The product has a fixed size of 13 ½″ long and 5″ wide at the rear end. Due to its narrow rear end, the product turned easily in the tray so as to twist and damages the cables. In addition, Zimmer's fingers take time and effort to insert cables one after one therebetween in the cable puller.
There is a need for a better cable puller for the industry.